1. Field of the Art
The present invention relates to a novel optically active ritodrine compound which is effective for the treatment of threatened premature birth and threatened abortion as well as the treatment of dysmenorrhea.
2. Related Art
Ritodrine, (.+-.)-erythro-1-(p-hydroxyphenyl)-2-[2-(p-hydroxyphenyl)ethylamino]-1-pro panol, represented by the formula (I): ##STR1## is known to be effective in preventing premature birth owing to its excellent activity for suppressing uterine contraction (Japanese Patent Publication Nos. 10139/1968, 21810/1970 and 22732/1970).
Each of the erythro and threo types of ritodrine structure was anticipated to have two kinds of isomers because of asymmetric carbon atoms at 1- and 2-positions. However, since ritodrine is the racemate of the erythro type ((.+-.)-isomer, specific rotation [.alpha.].sub.D.sup.25 =0.degree.) and the method for obtaining individually the (-)- and (+)-isomers has not been generalized, optically active ritodrines could not be obtained easily.
Therefore, the efficacies or the relationship with side effect of the isomers remained ambiguous and could not be examined. Ritodrines had problems to be solved including the examination of the properties of ritodrine isomers and of their possibilities as medicines, because ritodrines had side effects including an increase in heart rate.